This invention relates to the separation of single sheets from a stack in preparation for withdrawal thereof during an automatic sheet handling operation.
The automatic withdrawal of single flexible sheets from a magazine stack by a mechanical gripper mechanism is well known, for example, in connection with the sheet collating operations in a "Phillipsburg Inserter". In such apparatus, the bottom sheet of the stack at a collating station is deflected by a vacuum cup device and held separated from the stack by a pivoted finger in preparation for clamping of the separated portion of the bottom sheet to a gripper lever. The bottom sheet is thereby withdrawn by the gripper lever from the magazine and dropped onto a collating conveyor. Such collating operations are shown, for example, in U.S. Pat. No. 3,371,331.
The use of pressurized air flow for sheet separation is also known, as disclosed for example in U.S. Pat. Nos. 2,743,923, 2,806,696 and 2,979,329. In all of such prior art arrangements, the reliance on a remote source of suction pressure and/or moving parts in the sheet separating operation are sources of malfunction which reduces operational reliability, calls for relatively frequent repair and maintenance, and is costly to replace and install.
It is therefore an important object of the present invention to provide a less costly, more efficient and reliable sheet separating method and apparatus which avoids the use of mechanically moving parts.